<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        #big{
            width: 900px;
            height: 700px;
            border: 1px black dashed;
        }
        .top{
            width: 900px;
            height: 180px;
        }
        .d1{
            width: 100px;
            height: 150px;
            border: 1px black dashed;float: left;
            margin-left: 20px;
            padding-left: 20px;
            padding-top: 20px;
        }
    </style>
</head>
<body>
    <div id="big">
        <div class="top">
            <div class="d1">A</A></div>
            <div class="d1">A</div>
            <div class="d1">A</div>
            <div class="d1">A</div>
        </div>
        <div class="top">
            <div class="d1">A</div>
            <div class="d1">A</div>
            <div class="d1">A</div>
            <div class="d1">A</div>
        </div>
        <div class="top">
            <div class="d1">A</div>
            <div class="d1">A</div>
            <div class="d1">A</div>
            <div class="d1">A</div>
        </div>
    </div>
</body>
</html>